- First let's look at the energy aspect:
Your body has three energy stores: glycogen, fat and muscle. Free glucose is not an energy store.
Glycogen is refilled with carbohydrates and you can store 200-400g of it in your liver and muscle. It gets used for quick energy bursts (anaerobic), for regular energy and for keeping your blood glucose level up (mostly needed for the brain). You can deplete the entire store quite easily within a day.
(some people (including me) take this as a sign that carbs should not be a major part of your diet)
Our fat stores, even when lean, hold tens to hundreds of thousands of kcal, literally a month or more of energy. It provides energy at a slower rate than glycogen does for the same oxygen intake.
I list muscle for completeness. The body will break down muscle for energy and/or for the protein so if you like your muscles make sure to eat at least 20g protein/day (IIRC).
When you only eat one meal a day your metabolism will be very fat-dominant, which is perfectly fine. If you are very active, you may deplete your glycogen stores before you refill them at meal time. Your maximum power will be a little less and you won't be able to be as bursty. Your liver will start to make glucose from protein. If there is no protein available, muscle breakdown will occur.
- Now let's look at the health aspect:
When you fast for more than 12-16 hours, your cells start doing housekeeping. This is a good thing with many health benefits. See also here.
If you feel fine, keep doing it. After heavy exercise, consider a banana to refill glycogen.